Method of preparing a potato based food product

ABSTRACT

The present invention discloses a method of preparing a potato based food product, the method comprising the steps of: processing potatoes into potato articles having a desired size and shape, blanching said potato articles; coating said blanched potato articles with an emulsion, said emulsion containing starch; drying said emulsion coated potato articles; introducing said dried and coated potato articles into an elevated temperature environment for a predetermined period of time; removing said potato articles from said environment and allowing said articles to cool; and packing said articles.

The present invention relates to the preparation of a food product andin particular to the preparation of a potato based food product.

One method of preparing par-cooked potato product, such as chips, is towash, cut and blanch the raw potato, dry by about 10% and par-fry forabout 3 minutes at 140° C. Such chips are then cooled and bagged readyfor chilling or freezing. Such par-cooked chips are typically fried tocomplete the cooking process. This method permits rapid preparation ofchips for the plate and such chips have acceptable taste and mouth feel.Par-cooking by frying results in a relatively high final fat content,which it would be desirable to reduce.

According to the present invention there is provided a method ofpreparing a potato based food product, the method comprising the stepsof:

-   -   processing potatoes into potato articles having a desired size        and shape, blanching said potato articles;    -   coating said blanched potato articles with an emulsion, said        emulsion containing starch;    -   drying said emulsion coated potato articles;    -   introducing said dried and coated potato articles into an        elevated temperature environment for a predetermined period of        time;    -   removing said potato articles from said environment and allowing        said articles to cool; and    -   packing said articles.

It will be appreciated that the present invention avoids the frying ofthe potato articles in oil. The present invention thus enables thepreparation of par-cooked potato articles which have an acceptableeating quality yet have a much lower fat content than similar potatoarticles prepared by conventional par-cooking methods. The minimal fatcontent of the articles is governed by the fat content of the emulsion,the amount of emulsion added to the articles and dehydration of thearticles during the time spent in the elevated temperature environment.

The step of processing of said potatoes may comprise washing and peelingthe potatoes, followed by cutting into a desired shape such as, forexample, elongate sticks known as chips or fries. Typically chips orfries are made available in two sizes wherein the sticks have anapproximate cross-section of 8 mm square or 15 mm square, respectively.In an alternative embodiment the potatoes may be processed so as toprovide articles having a less regular shape. For example the potatoesmay remain substantially whole or, depending upon their size, may behalved or quartered after having been washed and peeled. Potatoes whichhave been processed thus may form the basis for roast potato articles.In yet a further alternative the potatoes may be washed and then cutinto wedge shapes with their skin left on.

Blanching of the potato articles may comprise blanching at asubstantially uniform temperature for a predetermined time. In such anembodiment the blanching temperature may be in the range of 70° C. to95° C., while the predetermined time may be in the range of 5 minutes to20 minutes. More preferably the blanching temperature may be in therange of 75° C. to 90° C., while the predetermined time may be in therange of 9 minutes to 16 minutes.

Alternatively the blanching step may comprise the utilisation of asuccession of differing blanching temperatures for different timeperiods. In such an alternative embodiment the blanching step maycomprise blanching at a first temperature for a first time periodfollowed by blanching at a second temperature for a second time periodwherein the second temperature is less than the first temperature andthe second time period is greater than the first time period. A thirdblanching procedure may follow the second blanching procedure. Such athird blanching procedure comprises blanching the potato articles at athird temperature for a third time period. The third temperature may bebetween the first and second temperatures while the third time periodmay be longer than the first time period but shorter than the secondtime period.

The first temperature may be in range of 85° C. to 100° C. with thefirst time period being in the range of 20 seconds to 90 seconds. Morepreferably the first temperature may be in range of 90° C. to 95° C.with the first time period being in the range of 30 seconds to 60seconds. The second temperature may be in range of 55° C. to 75° C. withthe second time period being in the range of 10 minutes to 25 minutes.More preferably the second temperature may be in range of 60° C. to 70°C. with the second time period being in the range of 15 minutes to 20minutes. The third temperature may be in range of 80° C. to 95° C. withthe third time period being in the range of 2 minutes to 10 minutes.More preferably the third temperature may be in range of 85° C. to 90°C. with the third time period being in the range of 3 minutes to 9minutes.

The blanched potato articles may advantageously be cooled after theblanching step. Cooling may be effected by any appropriate means suchas, for example, immersing the potato articles in cold water.

The method may advantageously include the step of partially drying saidpotato articles intermediate said blanching and coating steps. Thepartial drying may be effected by any appropriate means. Drying may beeffected by the use of heated air. The air may be heated to atemperature of between 70° C. to 110° C.

The emulsion comprises a mixture of water, oil and starch. Otheremulsion components may comprise any or all of the following: citricacid, colouring, sorbic acid, salt, egg, sugar, skimmed milk powder,stabiliser and emulsifier. Other food acids which may be included in theemulsion include acetic acid, lactic acid, malic acid, tartaric acid,hydrochloric acid, phosphoric acid and benzoic acid.

The emulsion may be heated prior to application to the potato articles.the emulsion may be applied by any appropriate means such as spraying.The articles may be agitated after being sprayed with the emulsion so asto ensure an even coating. In an alternative embodiment the potatoarticles may be dip coated with the emulsion. It will be appreciatedthat the emulsion is applied to, and remains on, the surface of thepotato article. The emulsion does not penetrate the potato article.

The coated articles may be dried, as described above, by the use ofheated air.

The step of introducing the coated potato articles into an elevatedtemperature environment may comprise placing the articles into an ovenor like heating apparatus. The oven may be a fan-type oven whichcirculates heated air over the articles. The elevated temperature may bein the region of 100° C. to 170° C. More preferably the temperature maybe in the region of 150° C. to 160° C. The time period during which thecoated articles may be subjected to said elevated temperature may be inthe range between 4 minutes to 40 minutes.

The drying steps of the invention may be quantified with reference tothe moisture content of the potato articles. More particularly, thedrying steps may be quantified with reference to a percentage increasein the dry matter (D.M.) content of the potato article.

Embodiments of the present invention will now be described by way ofillustrative examples.

EXAMPLE 1

Frying Chips 15 mm. 1. Pre-prepare mix for colouring batter:- g. Cumin100 Paprika 75 Turmeric 15

Mix is sufficient to prepare 700 kilos chips, so lower weight of thesame proportions of ingredients may be prepared for experimentalproduction. Colouring is not essential to the present invention, but maybe desirable. 2. Prepare batter for dipping chips:- g. Water 738Sunflower oil 112 Crisp Coat Starch 122 How 1 Stabilizer 4 Citric acid10 Salt 8 Skimmed milk powder 4 Colour pre-mix 2

How 1 stabilizer is available from G.C. Hahn & Co. of Lubeck, Germany.It includes Guargum (E412) and Xanthangum (E415). Crisp Coat Starch issupplied by National Starch & Chemical Co., Manchester, England.

3. Mix batter with high speed stirrer. If batter stands for more thanone hour after mixing, re-stir. The batter is a relatively unstableemulsion.

4. Prepare chips. Use potatoes of high dry matter over 21%. Preferredvarieties are Maris Piper, Russett Burbank, Agra, Asterix, Binge,Saturna. Peel, chip at 15 mm. cross section, remove slivers and nubbins.

5. Blanch 1 minute @ 95° C.

6. Blanch 15 minutes @ 70° C.

7. Blanch 8 minutes @ 90° C.

8. Dry to remove surface moisture from chips. Typically 5 minutes @ 100°C. Weight of 1 kilo raw chips after blanch & dry is typically 995 grams.

9. Stand chips to cool to 40° C. This typically takes a few minutes.

10. Dip in batter for 30 seconds and drain well. Weight of chipsincreases by about 6.5% to typically 1052 grams. As an alternative, forall examples, a desired weight of batter may be sprayed, and the productgently tumbled to give an even coating.

11. Dry such that chips have about 30.5% dry matter. In preliminaryresearch, potatoes used had 22.5% dry matter. These were dried to remove26%. The percentage reduction of potatoes of other dry matters may becalculated accordingly. In development, drying was done in air at 100°C. in domestic fan oven. The drying time in this method wasapproximately 40 minutes. Drying could be much quicker on specialiseddrying plant with higher air flow.

12. Par-cook chips for 10 minutes at 150° C. Weight will typicallyreduce to 682 grams.

13. Cool to 75° C., then fill into bags made for example from lowpermeability film, such as Pvdc coated polyester/polyethene. Bags aretypically flushed with carbon dioxide, then sealed.

Chips contain about 0.73% calculated fat content.

The recommended fry before eating is 3 minutes @ 190° C.

EXAMPLE 2

Frying Chips 8 mm.

1. Use colour pre-mix as for 15 mm chips. 2. Prepare batter for dippingchips:- g. Water 771 Sunflower oil 100 Crisp Coat Starch 100 How 1Stabilizer 4 Citric acid 6 Lactic acid 4 Skimmed milk powder 5 Salt 8Colour pre-mix 2

3. Mix batter with high speed stirrer. If batter stands for more thanone hour after mixing, re-stir. The batter is a relatively unstableemulsion.

4. Prepare chips. Use potatoes of high dry matter over 21%. Preferredvarieties are Maris Piper, Russett Burbank, Agria, Asterix, Bintje,Saturna. Peel, chip at 8 mm. cross section, remove slivers and nubbins.

5. Blanch 1 minute @ 90° C.

6. Blanch 15 minutes @ 65° C.

7. Blanch 4 minutes @ 85° C.

8. Cool in cold running water.

9. Dry 5 minutes @ 100° C. Weight of 1000 g raw chips after blanch isabout 1012 g.

10. Cool 2 minutes. Weight reduces to about 1008 g.

11. Dip in batter for 30 seconds. Drain well to remove excess batter.Weight after dip is about 1080 grams, an increase of 7.2%.

12. Dry such that chips have 30% dry matter. In preliminary research,potatoes with 22.5% dry matter were used, so weight is reduced by about25%. Equivalent calculations should be made for potatoes of other drymatters. The weight reduction was achieved by drying in fan over for 20minutes. Weight after dry about 750 grams.

13. Par-cook chips for 6 minutes at 150° C. Weight after cook is about307 grams., 61.7% of raw weight

14. Cool to 75° C., then fill into bags made from e.g. low permeabilityfilm. Bags are typically flushed with carbon dioxide, then sealed.

The chips contain 1.0% fat.

The recommended final flying time is 2 minutes @ 180° C. The weight lossin fry is 35% and the fat uptake is 7% of weight of chips put in frier.The total fat content of fries on plate is 11.0%.

EXAMPLE 3

Roast Potatoes

1. Use colour pre-mix as specified for 15 mm chips. 2. Make batter fordip (stir as necessary to maintain emulsion):- g. Water 458.5 Beaten egg255 Sunflower oil 136 Crisp Coat Starch 85 How 1 Stabilizer 3.5 Colourpre-mix 2.5 Citric acid 8.5 Hydrochloric acid 32% 10 Salt 10 Sugar 34

3. Peel potatoes and cut into pieces approximately rectangular withaverage weight of 50 g each.

4. Blanch 9 minutes @ 90° C. 1000 g. raw weigh about 1012 g afterblanch.

5. Cool in cold running water and dry 5 minutes @ 120° C. Weight afterdry about 995 g.

6. Dip for 30 seconds in batter and drain well. Weight after dip about1041 grams. gain of 4.6%.

7. Dry to reduce weight by 25% at 120° C. In a domestic fan oven thistakes 1 hour 30 minutes. Drying could be much quicker in commercialdrier.

8. Cook 10 minutes in oven at 150° C. Weight after cook about 720 grams.

9. Cool to 75° C., then fill into bags as used for chips, flush withcarbon dioxide, and seal.

10. To re-heat, spread on tray in oven and cook 15 minutes @ 200° C.

Fat content of roast potatoes 0.7%.

EXAMPLE 4

Oven Chips 15 mm

1. Use colour pre-mix as specified for 15 mm Frying Chips. 2. Preparebatter for dipping chips:- g. Water 640 Sunflower oil 202 Crisp CoatStarch 134 How 1 Stabilizer 2 Skimmed milk powder 5 Colour pre-mix 2Citric acid 9 Salt 6

3. Mix batter with high speed stirrer. If batter stands for more thanone hour after mixing, re-stir. The batter is an unstable emulsion.

4. Prepare chips. Use potatoes of high dry matter over 21%. Preferredvarieties are Maris Piper, Russell Burbank, Agria, Asterix, Bintje,Saturna. Peel, chip at 15 mm. cross section, remove slivers and nubbins.

5. Blanch 12 minutes @ 90° C. Wash in running water to cool.

6. Dry for 5 minutes @ 100° C. to surface dry.

7. Dip in batter for 30 seconds and drain well. Weight increase indipping 5.4%.

8. Dry to 100° C. to reduce weight by 25%. In domestic fan oven thedrying time is 50 minutes. Drying is likely to be much quicker ifcommercial drier is used

9. Cook @ 160° C. for 10 minutes. Weight after cook is about 65% of rawweight.

10. Cool to 75° C., then fill into bags made from low permeability film,for example pvdc coated polyester/olyethylene. Bags are typicallyflushed with carbon dioxide, then sealed

11. A recommended cooking procedure is to spread chips thinly on pan andoven cook for 15 minutes @ 200° C.

Fat content of chips is 1.2%. After cooking in oven as above the fatcontent of chips on plate is 1.7%.

EXAMPLE 5

Frying Chips and Oven Chips 15 mm

1. POTATOES

-   -   Variety: Maris Piper. Dry matter (DM): 24%. Reducing sugars very        low. Heavy surface bruising removed in hand peeling.        2. PREPARATION    -   Hand peeled. Chipped on hand operated chipper with 15 mm grid.        Slivers and nubbins removed by hand.

3. BLANCHING AND DRYING

Any blanching technique is appropriate given that the objective ofgiving maximum flesh softening without surface breakdown or scuffing isachieved.

The blanch technique used was

1 minute @ 95° C.

20 minutes @ 65° C.

9 minutes @ 85° C.

Cool in running cold water

Dry surface of chip prior to coating, e.g. by putting in fan oven for 3mins @ 100° C. 4. COATING MIX The mix for one kilo of coating was:- g.Water 532 Sunflower oil 246 Starch 91 Citric acid 16 Colour pre-mix 3.5Hamultop emulsifier 9 How 1 Stabilizer 2 Sorbic 27.5 Salt 73

The colour pre-mix was made by mixing:—parts parts Cumin 10 Paprika 7.5Turmeric 1.5

All ingredients for the coating mix are put into a beaker and mixed withhand held high speed stirrer until stable emulsion is formed. The mixwill remain sterile and keep for long periods if kept in air tightcontainer and briefly re-stirred before use.

The starch used is Crisp Coat UC starch supplied by National Starch &Chemical Co., Manchester. The stabiliser and emulsifier are made by G.C.Hahn & Co., Lubeck, Germany. Hamultop is the trade name of an emulsifiermade by G.C. Hahn Limited which includes concentrated whey powder.

The coating mix is intended to give extended shelf life to chips storedat ambient or chilled temperatures. If chips are to be stored anddistributed frozen the Citric and sorbic acids may be omitted from theemulsion.

5. APPLICATION of EMULSION COATING

Emulsion is added to prepared chips at the rate of 5% of chip weight. Ina continuous process this may be done by the combination of load cellsand spraying. After spraying chips should be gently moved around toensure an even coating of every chip. The dipping of chips in emulsionis not recommended for those to which acid is to be applied.

6. DRYING

After coating, chips are dried. Using the potatoes with 24% DM dryingshould continue till weight is reduced by 20% to give 30% DM. Ifpotatoes of other DM's are used drying should be adjusted to give 30%.

7. HOT AIR TREATMENT

Immediately after drying when still warm chips are transferred to adomestic oven at 150° C. where they are held for 9 minutes. In acommercial situation a continuous oven may be appropriate, such as usedfor biscuit making. The temperature of about 150° is important. Iftemperature is significantly lower the light texture inside the chip isnot achieved. If significantly higher the tips of the chips burn. Weightof chip is reduced by 29% of weight prior to dipping giving DM of 33.8%in finished chip.

8. PACKING

Chips are cooled after Hot Air treatment to about 60° C. and packed, forexample with a CO₂ flush. 9. FAT CONTENT OF CHIPS Calculatedmathematically % Fat content of emulsion 24.6 Fat content of chips given5% addition of above 1.23 Fat content of chips after losing 29% weightin heating 1.7310. FINAL PREPARATION BY CUSTOMER

Recommended methods are:

-   -   a) Fry chips. Three minutes in oil @ 180° C.    -   b) Oven chips. 10 minutes in oven @ 200° C.

EXAMPLE 6

Frying Chips 8 mm

1. POTATOES

Same as used for Example 5.

2. PREPARATION

Same as for Example 5 but chipped to 8 mm.

3. BLANCHING AND DRYING

Prepared chips were blanched:—

30 seconds @ 90° C.

15 minutes @ 60° C.

3 minutes @ 85° C.

Chips were then dried for 3 minutes @ 100° C. 4. COATING MIX The mixused to make one kilo was:- g. Water 603 Sunflower oil 204 Starch 90Citric acid 9 Colour pre-mix 2 Hamultop emulsifier 10 Sorbic 18 How 1Stabilizer 4 Salt 60

The colour pre-mix is the same as for Example 5. Ingredients are mixedas described for Example 5 and sources are the same.

5. APPLICATION of EMULSION COATING

Emulsion is added to prepared chips at the rate of 8% of chip weight.

6. DRYING

Dry to reduce weight before coating by 23% by drying in air @ 100° C.Chip has DM of 37.5%.

7. HOT AIR TREATMENT

Hot air treatment of 5 minutes at 150° C. Weight loss from chip beforedrying 36% giving DM of 37.5%.

8. PACKING

As for Example 5. 9. FAT CONTENT OF CHIPS Calculated mathematically %Fat content of emulsion 20.4 Fat content of chips given 8% addition 1.63Fat content of chips after losing 36% weight 2.55 in heat process10. FINAL PREPARATION

Recommended 2.5 minutes frying in oil @ 180° C.

EXAMPLE 7

Roast Potatoes

1. POTATOES

Same as used for Examples 5 and 6. After peeling cut into pieces ofapproximately 40 mm cross section.

2. BLANCHING

Blanch 16 minutes @ about 85° C. The blanching technique is important.It should soften the flesh of the potato without gelatanizing starches,making them sticky.

Surface dry potato by putting in fan oven for 3 minutes @ 100° C. 4.COATING EMULSION The mix used to make one kilo was:- g. Water 240Sunflower oil 250 Beaten egg 240 Starch 100 Roast potato colour pre-mix4 Citric acid 40 Salt 80 Hamultop emulsifier 9.5 How 1 Stabilizer 0.5Sorbic acid 36

Roast potato colour pre-mix contains:— parts Cumin 4 Paprika 4 Turmeric2

Emulsion is heated and maintained @ 40° C. and added to potato pieces atthe rate of 2.5% of potato weight, and potatoes gently tumbled to ensureeven coating over the whole surface.

4. DRYING

Dry to reduce weight of potato by about 25% giving 32% DM using potatoeswith 24% DM. Using potatoes with other raw DM's calculate loss requiredto give 32% DM.

5. HOT AIR TREATMENT

Immediately after drying when still warm, transfer to fan oven at 150°C. where they are held for 20 minutes. Weight of potato is reduced byabout 32.5% to 35.6%. DM

6. PACKING

As for Example 5. 7. FAT CONTENT OF CHIPS Calculated mathematically %Fat content of emulsion;-;- Sunflower oil 25.00 Egg content 24% with fat@ 12.3 grams/100 3.00 28.00 Fat content with 2.5% emulsion 0.70 Fatcontent after drying 32.5% 1.048. FINAL PREPARATION BY CUSTOMER

Recommended 10 minutes in oven @ 200° C. This is considerably shortertime than for existing products, and is believed to be due to theaddition of egg to the emulsion causing browning and crisping whenbaked.

1. A method of preparing a potato based food product, the methodcomprising the steps of: processing potatoes into potato articles havinga desired size and shape; blanching the potato articles; coating theblanched potato articles with an emulsion, the emulsion containingstarch; at least partially drying the emulsion coated potato articles;introducing the at least partially dried and coated potato articles intoan elevated temperature environment for a predetermined period of time;removing the potato articles from the environment and allowing thepotato articles to cool; and packing the potato articles.
 2. The methodof claim 1, wherein the step of processing the potatoes compriseswashing and peeling the potatoes, followed by cutting the potatoes intothe potato articles.
 3. The method of claim 2, wherein the potatoes arecut into elongate sticks known as chips or fries.
 4. The method of claim3, wherein the elongate sticks have a cross-section of about 8 mmsquare.
 5. The method of claim 3, wherein the elongate sticks have across-section of about 15 mm square.
 6. The method of claim 1, whereinthe blanching step comprises the utilisation of a succession ofdiffering blanching temperatures for different time periods.
 7. Themethod of claim 6 wherein the blanching step comprises blanching at afirst temperature for a first time period followed by blanching at asecond temperature for a second time period wherein the secondtemperature is less than the first temperature and the second timeperiod is greater than the first time period.
 8. The method of claim 7,wherein the blanching step further comprises a third blanching procedurefollowing the second blanching procedure, the third blanching procedureincluding blanching the potato articles at a third temperature for athird time period.
 9. The method of claim 8, wherein the thirdtemperature is between the first and second temperatures and the thirdtime period is longer than the first time period and shorter than thesecond time period.
 10. The method of claim 7, wherein the firsttemperature is in a range of 85° C. to 100° C.
 11. The method of claim10, wherein the first temperature is in a range of 90° C. to 95° C. 12.The method of claim 7, wherein the second temperature is in a range of55° C. to 75° C.
 13. The method of claim 12, wherein the secondtemperature is in a range of 60° C. to 70° C.
 14. The method of claim 9,wherein the third temperature is in a range of 80° C. to 90° C.
 15. Themethod of claim 14, wherein the third temperature is in a range of 85°C. to 90° C.
 16. The method of claim 2, wherein the desired shape is arounded shape.
 17. The method of claim 3, wherein the blanching stepcomprises blanching at a substantially uniform temperature for apredetermined time.
 18. The method of claim 17, wherein the blanchingtemperature is in a range of 80° C. to 95° C.
 19. The method of claim18, wherein the blanching temperature is in a range of 85° C. to 90° C.20. The method of claim 1, wherein the blanched potato articles arecooled after the blanching step.
 21. The method of claim 20 whereincooling is effected by immersing the potato articles in cold water. 22.(cancelled)
 23. The method of claim 36, wherein the partial drying iseffected by utilising heated air.
 24. The method of claim 23, whereinthe air is heated to a temperature of between 90° C. and 110° C.
 25. Themethod of claim 1, wherein the emulsion comprises a mixture of water,oil and starch.
 26. The method of claim 25, wherein the emulsionincludes at least one ingredient selected from the group consisting ofcitric acid, colouring, sorbic acid, salt, egg, sugar, skimmed milkpowder, stabiliser, emulsifier and hydrochloric acid.
 27. The method ofclaim 1, wherein the emulsion is heated prior to the coating step. 28.The method of claim 1, wherein the coating step includes spraying theemulsion on the potato articles.
 29. The method of claim 28, furthercomprising agitating the potato articles after spraying the potatoarticles with the emulsion.
 30. The method of claims 1, wherein thecoating step includes dip coating the potato articles with the emulsion.31. The method of claim 1, wherein the step of introducing the coatedpotato articles into the elevated temperature environment comprisesplacing the potato articles into a heated apparatus.
 32. The method ofclaim 31, wherein the heated apparatus is a fan-type oven whichcirculates heated air over the potato articles.
 33. The method of claim1, wherein the elevated temperature environment has a temperature in arange of 100° C. to 170° C.
 34. The method of claim 33, wherein thetemperature is in a range of 150° C. to 160° C.
 35. The method of claim1, wherein the predetermined period of time is in a range between 4minutes and 40 minutes.
 36. A method of preparing a potato based foodproduct, the method comprising the steps of: processing potatoes intopotato articles having a desired size and shape; blanching the potatoarticles; partially drying the blanched potato articles; coating thepartially dried and blanched potato articles with an emulsion, theemulsion containing starch; introducing the at least partially dried andcoated potato articles into an elevated temperature environment for apredetermined period of time; removing the potato articles from theenvironment and allowing the potato articles to cool; and packing thepotato articles.
 37. The method of claim 10, wherein the first timeperiod is in a range of 20 seconds to 90 seconds.
 38. The method ofclaim 11, wherein the first time period is in a range of 30 seconds to60 seconds.
 39. The method of claim 12, wherein the second time periodis in a range of 10 minutes to 25 minutes.
 40. The method of claim 13,wherein the second time period is in a range of 15 minutes to 20minutes.
 41. The method of claim 14, wherein the third time period is ina range of 2 minutes to 10 minutes.
 42. The method of claim 15, whereinthe third time period is in a range of 3 minutes to 9 minutes.
 43. Themethod of claim 18, wherein the predetermined time is in a range of 5minutes td 20 minutes.
 44. The method of claim 19, wherein thepredetermined time is in a range of 9 minutes to 16 minutes.